The present invention relates to the fabrication of filament-reinforced parts, wherein the part typically has a central core member and a filament matrix placed by a wrapping or winding process about the exterior surface of the core member.
The strength of the part results from the number and orientation of the filaments which form the filament matrix. The core member is typically formed from lightweight foam, fiberglass roving, chopped fiberglass matting, balsa, or other core materials well known to the art. The filaments are typically formed from minute discrete strands of fiberglass, carbon fiber, or other high strength low weight fibrous material, well known to the art.
The filament matrix is dimensionally stabilized relative to the core member by being immersed within a thermosetting resin, the resin also contributing to the overall strength of the part. It is well recognized that the resin may be applied to the filament matrix after the matrix has been wound about the part, or by passage of the filaments through a bath of unreacted resin prior to winding, or by other methods well known to the art whereby the filament matrix is wetted with the thermosetting resin before, during, or after application to the core member.
At least a portion of the filament matrix may be preformed prior to attachment to the coremember, such as by the use of cloths or tapes already having a multiplicity of filaments oriented in a desired array, as is well known to the art. Alternatively, the filament matrix may be formed directly on the core member by winding a single filament about the member to form several layers, each layer typically having a different filament orientation than the previous layer.
It should be noted that manual placement of cloth over a large surface area is more labor intensive than the automated winding of a single filament or tape about a core member having a simple shape. Composite parts, such as propeller blades and submarine periscope masts for example, are therefore now being efficiently fabricated by use of automated equipment that places the filament matrix against the core member by a winding process.
Automated fabrication of these parts is limited however to parts that do not have recesses formed in their exterior surfaces. If the filament matrix is wound about a part having surface recesses the filament matrix will "bridge over" these recesses, which will cause undesirable voids to form between the filament matrix and the recessed surface of the part.
No inexpensive method exists for the mass production of filament-reinforced parts having recesses formed in their exterior surface.
A method and apparatus therefore needs to be developed that allows for the inexpensive fabrication of parts having surface recesses by use of a filament matrix placement process.